With recent advancement of digital technologies in electronic devices, there has been increasing demands for an increase in a capacity of a non-volatile variable resistance element, a reduction in write electric power of the non-volatile variable resistance element, a reduction in write/read time of the non-volatile variable resistance element, and a longer life of the non-volatile variable resistance element, for storing data such as images. Under the circumstances in which there are such demands, it is said that there is a limitation on miniaturization of an existing flash memory using a floating gate.
As a first prior art which has a potential of meeting the above-mentioned demands, there has been proposed a non-volatile variable resistance element comprising a perovskite material (e.g., Pr(1-x)CaxMnO3 [PCMO], LaSrMnO3 [LSMO], GdBaCoxOy [GBCO], or the like) (see Patent Literature 1). In this technique, voltage pulses (wave-shaped voltages each having a short duration) which are different in polarity are applied to the perovskite material to increase or decrease its resistance value, and data are made to correspond to the changed resistance value, thereby storing the data.
As a second prior art which makes it possible to switch the resistance value using voltage pulses with the same polarity, there has also been proposed a non-volatile variable resistance element which utilizes a phenomenon in which a resistance value of a layer comprising transition metal oxide (NiO, V2O, ZnO, Nb2O5, TiO2, WO3, or CoO) changes by applying voltage pulses which are different in pulse width to this transition metal oxide layer (see Patent Literature 2). In conjunction with a variable resistance element using the transition metal oxide layer, a configuration in which cross-point memory arrays incorporating diodes are stacked together is put into practice.